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[Valsp]

From the official workshop manual for the Interceptor

Current from the alternator is also stored in a high capacity electrolytic capacitor which ensures that the engine can be started and run with a discharged battery or without a battery in the circuit

Note that contrary to what has been stated above it was fitted to allow starting with a flat battery as well as without a battery fitted

[Dennis C]

It's threads like this that have made my posts on here very infrequent, as some of you may possibly remember, I spent my entire working life in electronics and can categorically say that Revband is correct, there is no way that hanging a capacitor on to a flat battery will in any way aid starting, the capacitor will only have any affect if the battery is removed.

[Valsp]

Have you looked at the wiring diagram?

Its not hung across the battery.

[Dennis C]

Valsp, I think you need to have more practice reading circuit diagrams, yes I just looked, one end of the capacitor connects to the battery, the other end connects to the junction of the rectifiers and zenner diode this then connect to the other side of the battery via the ammeter and fuse, now this makes perfect sense because if the battery fuse were to fail the capacitor would still be in the charging circuit, non the less the capacitor IS in parallel with the battery.

[Valsp]

Thanks Dennis always happy to learn

I thought a zener diode only allowed current to run in the reverse direction when the Zener voltage was reached.

Doesn't that isolate the capacitor from the battery until the battery is up to voltage?

If not how could Enfield state that you did not have to isolate or remove the battey and it would run with a flat battery or a battery that had failed

[Dennis C]

You are close enough right regarding the zenner, when It's voltage is reached it will stop any further voltage rise, this normally is when the battery is charged and prevents over charging, no it won't isolate the capacitor, running this type of charging circuit without a battery or capacitor can damage the charging circuit itself therefore it is logical to put the capacitor on the primary side of the fuse, yes it can still run with a flat or bu**ered battery, if the battery is flat the bike will also be easier to start if the fuse is removed and then replaced when running.

[Valsp]

Thanks for your time Dennis

I now have a fuller understanding of how it works

[Alan R]

Hi guys------- the 2 key things to remember about fitting a Zenner diode are}--1) Make sure that it has good, clean, strong electrical contacts ie... no high resistance due to corrosion or loose clamping.......2) Ensure the finned, Aluminium body is placed in a constant flow of fresh air...Traditionally this will be under the fuel tank but ahead of the engine or near the frames' steering head............As I understand it and put in layman's terms}----The Zenner charging system has the Alternator giving it's max. output all the time......The Bikes system will demand "x" amount of Wattage depending on items in use-----the surplus amount of Watts is then dumped in the form of heat via the Zenner....Hence those huge fins on the containing body.............Modern day systems will "sense" the electrical demand made by the Bikes' system and control the Alternator's output to match that demand--hence no need for a Zenner...........I think that's about right ???

[Adrian]

That's pretty much it, Alan, no need for separate rectifier and Zener, all sone in one lump. I think the only Zener diode fitted RE's as standard would have been the later twins (Valsp's Interceptor) with the (better looking) flatter heat sink.



With high-output three phase alternators on modern bikes the standard regulator/rectifiers can now struggle to cope, hence the introduction of the mosfet reg/rectifier. An interesting read:



http://www.rexs-speedshop.com/epages/es ... regulators



A.

[NicoV]

Just for you information: I had read about this on Gurunandan's site (the Bullet guru in Bangalore): nandanmotors dot com. There is also an article about it here: http://www.snowvalley.20m.com/bikes/caps.htm